1. Field of the Invention
The present invention relates to a semiconductor device, more particularly, to a semiconductor device module including a structure in which a package having an integrated circuit (IC) chip mounted thereon, for example, a central processing unit (CPU), is connected to a leadless chip carrier (LCC) having mounted thereon, for example, an erasable programmable read only memory (EPROM), by means of a box-type holder into which the LCC is fitted and can be removed. The LCC is one which does not have, at its surface, any lead projections.
2. Description of the Prior Art
It is known to combine a CPU and EPROM to form an evaluation one-chip microcomputer. A desired program is written into the EPROM by cyclically carrying out a writing operation an evaluating operation, and an erasing operation by means of ultraviolet rays. Once a desired program is obtained in the EPROM, mask read only memories (mask ROM's) having the desired program are manufactured simultaneously with the manufacturing of the CPU so as to form commercially-used one-chip microcomputers.
Usually, the evaluation one-chip microcomputer or the commercially-used one-chip microcomputer is mounted on a substrate on which other devices of, for example, a random access memory (RAM), are also mounted.
Conventionally, an EPROM, even one formed as an LCC, is mounted on a package by soldering its electrodes to the electrodes of the package. When an evaluation one-chip microcomputer is assembled with other devices on the same substrate, as mentioned above, it is difficult to carry out the writing operation, the evaluation operation or the erasing operation. That is, in order to write a new program into the EPROM, the EPROM must be removed from the package or the evaluation one-chip microcomputer must be replaced by a new evaluation one-chip microcomputer having an EPROM into which a new program has been written. Removal of an EPROM from a package is almost impossible, while replacement of a one-chip microcomputer is very expensive.
Further, in a conventional evaluation one-chip microcomputer, the package having the EPROM and the CPU mounted thereon is referred to as a dual-in-line package. The EPROM is mounted on a portion of the dual-in-line package different from the portion where the CPU is mounted. Therefore, the conventional evaluation one-chip microcomputer has the problem of being large in size.
More generally, in semiconductor devices, it is often required to be able to easily replace one of the elements in a device by another element. For example, when one of the elements in a semiconductor device is destroyed, a new element must be added to replace the destroyed element. Also, for example, in order to obtain various functions in one semiconductor device, one or more elements may be simply replaced by another element.
Conventionally, however, semiconductor elements such as CPUs, RAMs, or analog-to-digital (A/D) converters, are fixedly mounted by, for example, soldering them on the device and they cannot be removed easily.